Railway track circuit apparatus



May 20, 1941.

A. G. WILLIAMSON 2,242,984 RAILWAY TRACK cmcun' APPARATUS Filed May 5, 1939 Jgynzzl Conzirol CLr'cuLfi X i h 15 4972a! Cmzral Czrc Lu. Z. 110w z 1212' Co'girol PB 3 i. 4/ M Circuii' 1? 5 30a 3940 Z I r ;.5'.? 3.3 .96 Check'onaci I, j 19 I INVENTOR 7%,} s21 42 43 4 36 I Hrba lliamson. 34 3.5 I Y v 4,5 l HIS ATTORNEY Patented May 20, 1941 RAIIIWAY TRACK CIRCUIT APPARATUS Arba G. Williamson, Carnegie, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a. corporation of Pennsylvania Application May 5, 1939, Serial No. 271,883

4 Claims.

My invention relates to railway track circuit apparatus.

An object of my invention is the provision of novel and improved means for providing a high shunting sensitivity for a. track circuit by substantially eliminating the usual necessary difference between the pick-up energy level and the drop-away energy level of the relay means. Another object of my invention is the provision of novel and improved means for a track circuit wherewith a train shunt once effective and the corresponding restrictive signal condition established, a subsequent intermittent loss of train shunt is ineffective to create a false clear signal condition. That is to say, a train shunt effective even intermittently retains the restrictive signal condition corresponding to occupancy of the track section in effect. Again, an object of my invention is the provision of a primary-secondary relay combination for a track circuit wherewith energy for but one relay is required at a time except for a momentary switching period. Other objects and advantages of my invention will appear as the specification progresses.

I shall describe three forms of apparatus embodylng my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawing, Figs. 1, 2 and 3 are diagrammatic views of three different forms of apparatus embodying my invention. In each of the different views like reference characters designate similar parts.

Referring to Fig. 1, the track rails la and lb of a stretch of railway over which traffic normally moves in the direction indicated by an arrow are formed by the usual insulated rail joints with a track section WX which may be one section of a series of consecutive sections of a signal system. Track section WX is provided with a track circuit comprising a source of current connected across the rails at one end of the section and a primary-secondary relay means connected across the rails at the other end of the section. The current source may be any convenient form for supplying either alternating current or direct current and in Fig. 1 the current source is a track battery 2 whose opposite terminals are connected with rails la and lb at the exit end of section WX over wires 3 and 4, a current limiting resistor 5 being preferably interposed in wire 3.

A primary relay PR and a secondary relay SR of a so-called primary-secondary relay combination are connected with the rails la and lb at the entrance end of section WX. The relays PR and SR are direct current neutral relays, the relay PR being characterized by a relatively low pick-up energy and slightly slow to release, and relay SR being characterized by a relatively high drop-away energy and slow to pick up. Preferably the pick-up energy level of primary relay PR and the drop-away energy level of secondary relay SR are substantially the same, and would be made substantially equal to the energy level effected by track battery 2 under wet ballast conditions for section WX with some margin to allow variations of battery voltage and other operating conditions.

The operating winding 6 of primary relay PR has one terminal connected with rail lb over wire I and its other terminal connected with rail la over wire 8, back contact 9 of relay SR and wire Ill. Hence relay PR is connected across the rails for energization from track battery 2 only when relay SR is released closing back contact 9. The relay SR is provided with a pick-up circuit and a stick circuit. The pick-up circuit for relay SR can be traced from a local battery I3 over front contact l2 of relay PR, wire l5, winding ll of relay SR, wire IS, a resistor l4 and to the other terminal of battery IS. The stick circuit for relay SR can be traced from the track battery 2 over wire 3, resistor 5, rail lb, wires 1 and I5, winding ll and front contact I! of relay SR, wire l0, rail la, wire 4 and to battery 2. Consequently, the secondary relay SR is picked up by current from the local current source l3 and is then connected across the rails and retained energized by the track battery 2. The two relays PR and SR cooperate to control a signal control circuit which as here shown includes a front contact l8 of relay SR and back contact IQ of relay PR.

When track section WX is unoccupied the primary relay PR is deenergized and released, and the secondary relay SR is energized and picked up, relay SR being energized by current supplied to its stick circuit by the track battery 2. Under .this normal condition of the relays the signal control circuit is closed. When a train enters section WX and shunts the track rails, the secondary relay SR is deenergized and released. Since relay SR is provided with a high drop-away energy, relay SR is released notwithstanding the train shunt resistance may be relatively high. That is to say, the track circuit for section WX has a high shunting sensitivity because of the relatively high drop-away ener y of relay SR. With relay SR. released the signal control circuit is opened at front contact I8 and the winding 6 of primary relay PR is connected across the rails due to the closing of back contact 9 of relay SR.

When the train vacates section WX, the primary relay PR is picked up by current supplied by track battery 2. It is to be recalled that relay PR is provided. with a relatively low pick-up energy, the pick-up energy level of relay PR being no higher than the drop-away energy level of the secondary relay SR. Hence, relay PR is effectively energized and picked up notwithstanding unfavorable ballast conditions may prevail. With relay PR picked up closing front contact I2, current is supplied from the local battery 13 to the winding i l of relay SR and relay SR is energized and picked up at the end of its slow pick-up period. Battery l3 and resistor M are so proportioned that the energy level of relay SR effected thereby is enough greater than the drop-away value of relay SR to assure reliable picking up of that relay, but that over-energization of relay SR is avoided. With relay SR picked up opening back contact 9 and closing front contact H, the primary relay PR isdisconnected from the rails and the secondary relay SR is connected thereto. Relay PR is now deenergized and releases at the end of its slow release period, and relay SR is retained energized by current supplied from the track battery 2. It should be observed that in switching the connection of relay SR from the local battery [3 to the track rails for receiving energy from the track battery 2, there is a moment when both front contact I2 of relay PR and front contact I! of relay SR are closed and winding H of relay SR may be supplied with current from either the local battery l3 or the track battery 2. The track battery 2 and the local battery I3 are poled so that there is no opposing of the energization of winding 1 I during the switching operation. When relay PR is released closing back contact I8 the signal control circuit is completed.

It should be observed that a momentary loss of train shunt which might cause relay PR to pick up does not result in a false closing of the signal control circuit unless the loss of train shunt persists for an interval greater than the summation of the slow pick-up period of the relay SR and the slow release period of relay PR. It is clear that in the event such protection against a momentary loss of train shunt is not required relay SR need not be slow to pick up in character. Furthermore, if contacts I! and 9 of relay SR be of the continuity transfer type so that the connection for primary relay PR is not opened be fore the connection for the secondary relay SR to the rails is closed, then the primary relay PR need not be slow releasing in character.

In Fig. 2, the track rails Ia and lb are formed with an insulated track section WX provided with a track circuit the same as in Fig. 1, the track circuit provided for section WX of Fig. 2 being supplied with current from track battery 2 connected across the rails at the exit end of the section and also with a primary-secondary relay combination connected across the rails at the entrance end of the section. In Fig. 2, the track battery 23 of the track circuit for the section next in the rear of section WX is shown, battery being connected across the rails of the section next in the rear over a current limiting resistor 2|. The primary relay PR and the secondary relay SR of Fig. 2 are the same as in Fig. 1 except both relays PR and SR of Fig. 2 are of the ordinary acting type and relay SR is provided with a continuity transfer contact. That is, relays PR and SR of Fig. 2 are characterized by relay SR having a drop-away energy level substantially equal to the pick-up energy level of relay PR. Winding 6 of relay PR of Fig. 2 has its left-hand terminal connected with rail lb over wire I, and its right-hand terminal connected with rail la over wire 5, back contact member 22 and trans fer contact member 23 of a continuity transfer contact for relay SR, and wire Hi. It follows that relay PR is connected across the rails for receiving energy from the track battery 2 only when relay SR is released closing contact 2223. The secondary relay SR of Fig. 2 is provided with a pick-up circuit and a stick circuit the same as in Fig. 1, the relay SR of Fig. 2 being normally energized over its stick circuit which can be traced from track battery 2, wire 3, resistor 5, rail lb, Wires 1 and I5, Winding l i of relay SR, front contact member 24 and transfer contact member 23 of relay SR, wire is, rail la, wire t andto battery 2. The pick-up circuit for relay SR of Fig. 2 extend from one terminal of track battery 20 as sociated with the track circuit of the section next in the rear, over an asymmetric unit 25, front contact l2 of relay PR, wire 15, winding H of relay SR, front contact 28 of relay PR, a resistor 21 and to the other terminal of battery 21]. The signal control circuit is controlled jointly by the relays SR and PR and includes front contact is of relay SR and back contact IQ of relay PR.

When section WX of Fig. 2 is unoccupied, relay SR is picked up and relay PR is released, relay SR being retained energized by current supplied from track battery 2. Under this normal condition of the relays the signal control circuit is closed. When a train enters section WX, the secondary relay SR is quickly released due to its relatively high dropaway energy. With relay SR released the signal circuit is opened at front contact l8 and winding 6 of the primary relay PR is connected across the rails due to the closing of the contact 22-23 of relay SR. When the train vacates the section the primary relay PR i picked up by current supplied by track battery 2, the primary relay PR being characterized by a relatively low pick-up energy as pointed out hereinbefore. With relay PR picked up closing front contacts 52 and 26, the pick-up circuit of relay SR is closed and relay SR is energized by current supplied by the track battery 20 for the section next in the rear. The resistor 2! is proportioned so that battery 28 provides sufiicient energy to reliably pick up the secondary relay SR but not over-energize that relay. When relay SR is picked up its winding II is connected acros the rails of the section WX due to the closing of contact 23-24 and relay SR is conditioned for energization by the track battery 2 of section WX. The primary relay PR is now disconnected from the rails due tothe opening of the contact 22--23 of relay SR. Due to the continuity transfer contact of relay SR the primary relay PR is not released to open the pickup circuit for relay SR until the latter relay is connected across the rails and conditioned for energization by the track battery 2. 'The batteries 2 and 20 are poled so that the currents supplied to relay SR by the two batteries during the switching period, that is, during the brief interval both relays PR and SR are picked up, add their effects. The asymmetric unit 25 is included in the pick-up circuit of the relay SR as an additional precaution against current flowing from track battery 2 to the track circuit for the section next in the rear. The asymmetric unit may not be needed. The arrangement of Fig. 2 avoids the necessity of any additional local battery. Since energy is required from the track battery 20 for relay SR only during the brief period of picking up relay SR, no undue additional load is placed on the track battery 20. It is clear that in Fig. 2 relay PR may be slow to release and relay SR may be slow to pick up if desired.

Referring to Fig. 3, the track rails la and lb are formed with an insulated track section WX provided with a track circuit the same as in the previous cases. Track battery 2 is connected across the rails at the eXit end of section W-X and a primary-secondary relay combination consisting of a primary relay PR and a secondary relay SRI is connected across the rails at the entrance end of the section. The primary relay PR of Fig. 3 is similar in characteristics to the primary relay PR of Fig. l. The secondary relay SR1 is preferably a direct current time element relay having an initial deenergized position and an operated position to which it is moved only when a winding of that relay has been energized for a predetermined period which period is, or-

dinarily at least, of a relatively long interval.

The relay SRi may take different forms and as shown in Fig. 3 it is of the construction covered by the United States Letters Patent No. 2

1,966,965, granted July 17, 1934, to Branko Lazich and I-Iarrey E. Ashworth for Electrical relays, and to which patent reference is made for a full understanding of such time element relay. For the present application it is sumcient to say that when the two portions a and 30b of an operating winding are alternately energized over a circuit to be later described, an armature 3| is oscillated back and forth at a predetermined rate to actuate a pawl 32 and drive a ratchet wheel 33 in a clockwise direction as viewed in Fig. 3. The ratchet wheel 33 when thus driven causes through a clutch not shown an arm 34 to be rotated in a step-by-step manner from an initial position to an operated position, arm 34 being provided with two contact actuating members 35 and 36. The arrangement is such that when the relay SRl is deenergized the arm 34 is released from ratchet wheel 33 and is biased by gravity to its initial position where contact member 35 engages a contact finger 31 and closes a check contact 37-38 checking the initial position of the relay. When the relay is energized as will shortly appear, arm 34 is engaged with ratchet wheel 33 and is rotated from its initial position in a step-by-step manner due to the movement of ratchet wheel 33, and if the movement is continued for a predetermined interval the contact member 36 causes a contact finger 39 to engage and close a time element contact 39-40, the interval required to move arm 34 from its initial position to its operated position being predetermined and readily adjustable by mechanism not shown but fully described in the aforementioned Patent No. 1,966,965. That is is say, when the operating winding 3lla30b is energized for a predetermined time interval the arm 34 is gradually moved from an initial position to an operated position, the check contact 3'l-38 being opened shortly after the movement is started and the time element contact 394ll being closed when the full operated position is reached.

When contact 39-40 is closed, a stick circuit to be later described for a holding winding 4lw-4lb of relay SRI is closed and that winding is energized along with the operating winding causing contact fingers 42, 43 and 46 of a neutral armature to be picked up from engagement with respective back contacts into engagement with respective front contacts. With the neutral armature picked up opening back contact 4244 the operating winding 3lla30b is deenergized and further operation of the ratchet 33 ceases but arm 34 is held at its operated position closing contact 39-40 and the contact fingers 42, 43 and 46 of the neutral armature are retained in engagement with their respective front contacts as long as the holding winding 4la4lb is energized. When holding winding 4la--4lb is deenergized the neutral armature falls to disengage the contact fingers 42 and 43 and 46 from their respective front contacts and to engage their respective back contacts, and the arm 34 at once drops back to its initial position closing the check contact 3l38 and opening contact 39-40. Furthermore, momentary deenergization of the operating winding Sta-30b at any place in the movement of arm 34 from its initial position to its operated position causes arm 34 to be released and to drop back to its initial position. It is to be seen, therefore, that relay SRI requires uninterrupted energization of its operating winding Mia-3% for a predetermined interval in order to move the operating arm 34 from its initial position to its operated position, and this predetermined interval is adjustable for any selected period within relatively wide limits, such as, for example, from a period of the order of ten seconds to a period of the order of five minutes. Relay SRI is retained at its operated position by energization of its holding winding 4la--4lb and is immediately restored to its initial position When the holding winding is deenergized.

As far as the holding winding of relay SRI is concerned, the relay SR! is characterized by a drop-away energy level which is substantially the same as the pick-up energy level of relay PR. That is, the relationship between the drop-away of contact fingers 42, 43 and 45 of relay SR! and the pick-up of relay PR of Fig. 3 is substantially the same as the relationship between the pri mary and secondary relays of Figs. 1 and 2.

In Fig, 3 the signal control circuit includes front contact 46-4? of relay SRl and back contact l9 of relay PR.

Under normal conditions and section WX of Fig. 3 unoccupied, the primary relay PR is deenergized and the secondary relay SRI is picked up by virtue of a stick circuit including its holding winding 4la-4ib and which circuit is supplied with current by the track battery 2. This stick circuit can be traced from track battery 2 over wire 3, resistor 5, track rail lb, wires 1 and 50, holding Winding 4la--4lb, contact 3940, wire l 6, track rail lb, wire 4 and back to track battery 2. When a train enters section W-X to shunt the track rails the secondary relay SR! is released, relay SR! being highly sensitive to the train shunt due to its relatively high drop-away energy. With relay SRI released the signal control circuit is opened at contact 464? and the holding winding 4 la;--4 lb is disconnected from the track rails by the opening of contact 39% while the winding 6 of primary relay PR is connected across'the track rails over a first circuit path including the check contact 3?38. To be explicit, winding 6 of relay PR has its left-hand terminal connected with rail lb over wire T and its right-hand terminal connected with rail la over a first circuit path including wire 5|, check contact 3'l-38 and wire Hi.

When the track section WX is vacated, primary relay PR is picked up by current supplied from track battery 2, it being recalled that relay PR is provided with a relatively low pick-up energy. When relay PR is picked up closing its front contact 52, a second circuit path is provided by which the right-hand terminal of winding 6 is connected with rail la and which path includes wire 5|, back contact 4345 of relay SPA, frontcontact 52 of relay PR'and wire Iil.

With relay PR, picked up closing front contact 22 a circuit is formed for energizing the operating winding of relay SRI from a local battery l3 and which circuit can be traced from battery I3 over front contact I?! of relay PR, back contact 42-44 of relay SRl, the two portions 39a and 30b of the operating winding alternately due. to the contact of armature 3| alternately short-circuiting the two portions 36a and 3% as will be readily understood by an inspection of Fig. 3, and thence back to battery [3. After a short movement of arm 34, the check contact 31-38 is opened but winding 6 of relay PR is still connected across the track rails over the second circuit path described above. After the lapse of the predetermined interval required to move arm 34 to its operated position, the contact member 36 causes contact 3940 to close and the holding winding of relay SR! is connected across the rails and receives energy from the track battery 2 over the stick circuit traced hereinbefore. When the holding winding is energized as well as the operating winding of relay SRI, the neutral armature is at once picked up after which the operating winding is deenergized due to the opening of back contact 62-44 leaving the relay SRI held energized by its holding winding due to current supplied thereto from the track battery 2. With 7 the picking up of the neutral armature of the relay SRI to open back contact 43-44, the winding 6 of the primary relay is disconnected from the rails and that relay is released at the end of its slightly slow releasing period. When relay PR is released to close back contact I9 the signal control circuit is again closed.

It is evident that in the event of a loss of train shunt and relay PR is picked up, the secondary relay SRI must be operated for a predetermined period before the relays PR and SRI are reset to close the signal control circuit, and if the train shunt is effective for even a brief period during such operating period relay SRI is at once restored to its initial position. Also, if the train shunt is effective even intermittently the relays PR and SR! are operated to retain the signal control'circuit in the condition corresponding to occupancy of the track section. v Although I have herein shown and described only three forms of railway track circuit appa ratus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a track circuit for an insulated railway track section, a source of track circuit current connected across the rails at one end of the'sec tion, a track relay, a time element relay having well as a contact actuating member moved slowly from a first position to a second position when said operating winding is energized for a predetermined period and retained at said second position when said holding winding is subsequently energized, means including a first position contact of said time element relay to connect a winding of said track relay across the rails at the other end of the section for energization of said track relay by said source of track circuit current, a local current source, means including a front contact of said track relay to connect said operating winding with said local source to energize said time element relay and operate said contact member, stick circuit means including a front contact of said track relay to connect said winding of the track relay across the rails of the section for energization of said track relay while said contact actuating member is being operated, and other means including a second position contact of the time element relay to connect said holding winding across the rails at said other end of the section for retaining said time element relay energized and said contact member at its second position in response to current supplied by said track current source.

2. In combination with a railway track section having a source of current connected across the rails at one end of the section, a track relay to be connected at times across the rails at the other end of the section, said relay shunted by the train shunt when the section is-occupied by a train and eifectively energized by said current source when the train shunt is removed, a time element relay having an initial position and an operated position and characterized by movement from its initial position'to its operated position in a relatively long predetermined interval when energized and by a relatively quick movement from its operated position back to its initial position when deenergized, a check contact for said time element relay closed only at the initial position, another contact for said time element relay closed only at the operated position, a signal circuit including said other contact, means including either a front contact of said track relay or said check contact to connect said track relay across the rails of the section, and other means including a front contact of said track relay to energize said time element relay for moving the relay from its initial'to its operated position so as to cause said signal circuit to be held open when said train shunt is intermittently effective at intervals spaced apart no greater than said predetermined time interval.

3. In combination with a railway track section having a source of current connected across the rails at one end of the section, a first relay to be connected at times across the rails at the other end of the section, said first relay shunted by the train shunt when the section is occupied by a train and effectively energized by said current source when the train shunt is removed, a time element relay having an initial position and an operated position, said time element relay characterized by a gradual movement from its initial position to its operated position in a predetermined relatively long interval when the relay is energized and a relatively quick movement back to its initial position when the relay is deenergized, a check contact for said time element relay closed only at the initial posi ion, other contacts for said time element closed only at the operated position, a circuit including either said check contact or a front contact of said first relay to connect the first relay across the rails of the section, a local current source, means including a front contact of said first relay and a back contact of said time element relay to connect said time element relay With said local current source for moving the time element relay to its operated position, other means including an operated position contact of the time element relay to connect the relay across the rails of the section to retain the relay energized from said first mentioned current source, and a signal circuit including an operated position contact of said time element relay.

4. In a track circuit for a track section having a source of track circuit current connected across the rails at one end of the section, the combination comprising, a first track relay, a second track relay having a contact actuating member which is moved slowly from a first position to a second position when an operating Winding is energized and is retained at said second position when a holding winding is subsequently energized, said second track relay also provided with front and back contacts controlled by said holding winding,

a first circuit path including a contact closed at said first position of the contact. actuating member to connect a winding of said first track relay across the rails at the other end of the section to pick up the first relay by current from said track circuit source, a second circuit path including a back contact of said second track relay and a front contact of said first track relay to connect the winding of the first relay with the rails of the section to energize the first relay by the track circuit source, a local current source, an operating circuit including a back contact of said second track relay and a front contact of said first track relay to connect said operating Winding with said local current source to operate said contact actuating member, a holding circuit including a second position contact of the contact actuating member to connect said holding winding across the rails of the section to retain said 

